A look at killer dolphins, plus hibernating plankton, growing mammal brains and more in this week’s news

Plankton sleep through apocalypse
Tiny photosynthetic organisms may have survived decades of darkness following the meteor crash that killed the dinosaurs by resting, Dutch and Portuguese researchers report online May 17 in Nature Communications. The group revived more recent plankton organisms trapped in the mud below Swedish fjords, concluding that such organisms can live for up to a century without sunlight. Like hibernating bears living off fat stores, these organisms seem to eat up stockpiles of food during rest. This behavior could explain how certain photosynthesizers survived the ancient meteor fallout even as many sunlight-dependent plants went extinct. —Daniel Strain

Smells like mammal brain
New scans of fossil skulls suggest that almost-mammal brains got their first boost toward supersizing from improved senses of smell, touch and muscle control. Mammals today boast the largest brains relative to body size among living animals, and ideas for what drove that brain boost have arisen from comparisons among modern species. To get a better look at the skimpy fossil record of skull cavities, U.S. researchers used high-resolution X-ray techniques to detect contours inside two tiny 200-million-year-old skulls from China. Adding this information to other anatomical data from fossils and living animals suggests the order in which various brain parts, and their functions, went big, the researchers suggest in the May 20 Science. —Susan Milius

Porpicide outbreak
Too much testosterone or too few lady dolphins may be playing a role in puzzling, violent attacks by bottlenose dolphins on harbor porpoises along the California coast.  Since 2005, bottlenose dolphins have killed at least 44 porpoises there. For the first time a research team documents details of three attacks and the necropsy of a victim. Almost all the dolphins involved were males. Fatal competition between the species seems unlikely, because their diets don’t overlap much, California researchers report in an upcoming Marine Mammal Science. Rough dolphin play or fighting practice still might be a factor, although attacks suspiciously tend to occur at the peak of the breeding season. —Susan Milius


Why eggs like company

View the video

Mother leaf beetles that prefer laying their eggs near other beetles’ eggs may be joining forces in a life-and-death fight against shrubbery. The evolutionary pressures that favor a tendency to aggregate have inspired a lot of scientific theorizing. But now researchers at Cornell have experimentally demonstrated a novel benefit of crowds. Eggs laid next to other leaf beetle eggs on twigs of viburnum shrubs were more likely to survive than loner clutches. The army of eggs had a better chance of killing the twig holding them, thus foiling the plant’s usual defense of growing tissue that crushes the insect eggs, the researchers say in the June Ecological Entomology . — Susan Milius

PLANT FIGHTS BACK from Science News on Vimeo.

It’s beetle versus bush when a mass of viburnum leaf beetle eggs (dark lump) starts developing under a rough, brown covering left by their mom. Video (one image per half-hour for three weeks) at first shows nothing more dangerous than a casual white mold frosting their covering, but then the plant’s response kicks in and breaks the egg pile. A strong plant defense may have favored beetle egg crowds that even out the fight.
Credit: Kent Loefler/Cornell University

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